1. Field of the Invention
This invention relates to a keyboard and an apparatus having the keyboard built therein used for a portable information processing apparatus, such as, for example, a notebook type personal computer or a word processor.
2. Description of the Related Art
Portable information processing apparatuses, referred to hereinafter as apparatuses, are particularly required to be easily handled when the lid is open for its operation and to be thin when the lid is closed.
There has been proposed a first solution, such as disclosed in Japanese Provisional Patent Publication Hei4-180115, where the apparatus has a lid connected to the main body via a hinge so as to freely open or close. The keyboard can ascend and descend in the main body when the lid is opened and closed, so that when the lid is opened the keyboard ascends from the inside of the main body. And, when the lid is closed the keyboard descends into the inside of the apparatus frame so as to be contained therein.
In order to meet the requirements there has been also proposed as a second solution an apparatus, such as disclosed in Japanese Provisional Patent Publication Hei8-549640. In this apparatus a vertical motion of key tops is supported and guided by a guide member, where the key tops are positioned at either of the below-described two positions by horizontally shifting a switching member carrying the guide member:
1) The key tops are positioned at a switching position, that is, the keys are in operation, when the lid is open; or
2) The key tops are positioned at a non-operating position which is lower than the switching position, when the lid is closed for being carried.
The first and second prior art apparatuses require to secure a space beforehand to contain the keyboard in the apparatus frame. Accordingly, the apparatus becomes thicker for the secured space.
A third solution is such as disclosed in Japanese Provisional Patent Publication Hei5-119884. In this apparatus is employed an air spring having the air sealed up therein, where the restoring of the pressed key is carried out with a piston and a cylinder. All of key cylinders are connected with each other via pipes so as to provide a sealed-up space, where is provided an opening/closing valve, via which there is allowed an sealing-up and an exhausting-out of the compressed air. When the air is exhausted there is no air in the sealed space so that all the key tops come down to the lowest position. When thekey board is in use, the air is introduced into the sealed space so that the keys come up to the highest position.
However, in this prior art apparatus, the keyboard not in use is at the lowest position due to the air exhausted. Therefore, the contacts of the key key switches are kept closed. As a result of keeping the contacts closed, the contacts are deteriorated.
A fourth solution is such that, when the apparatus is carried with the lid closed the lid pushes the keys so deeply as to fully depress the keys, whereby the apparatus becomes thin by this pushing-down stroke. However, in this prior art apparatus thus thinned by depression of the keys by the closing stroke of the lid, the spring for restoring the depressed key is also always compressed, resulting in fatigue.